Any none cryptic ways for working this out? How can the dot product be used? I know a formula for 2d angle calculating but i cant find any info for 3d? And what is R^2 exactly?

[itex]\Re^2[/itex] is (real) 2-space, or 2D. [itex]\Re^3[/itex] would be 3-space (3D) etc. None of the above post's were cryptic in the slightest (except the first one in which the author acknowledged was erroneous). What is the formula for calculating the cosine of the angle between any two vetors?

While this is the best, most succinct answer, I just want to make it clear that it really is the dot-product that answers the question:
[tex]\cos(\theta) = \frac{\vec a \cdot \vec b}{\sqrt{\vec a \cdot \vec a} \sqrt{\vec b \cdot \vec b}}[/tex]

While this is the best, most succinct answer, I just want to make it clear that it really is the dot-product that answers the question:
[tex]\cos(\theta) = \frac{\vec a \cdot \vec b}{\sqrt{\vec a \cdot \vec a} \sqrt{\vec b \cdot \vec b}}[/tex]

That's why: Dot's the answer.

Damn it! :grumpy: Sorry guys; I'm gona have to stop working at the same time as posting! It lucky that not too many of these errors crop up in my work